Such a data a communication method is known as a contention based access protocol, wherein transmitting data packets is released after detection that no signals are present in the wireless channel. In the case of any detected signal presence, transmission of the data packet is postponed to a predetermined later instant. At the later predetermined instant the detecting step is repeated and the data packet is transmitted if the channel is free of detected signals. Otherwise, the process is repeated again at a further later instant.
In practice, many devices might send signals in the shared wireless channel, such as radar equipment, microwave ovens, cordless phones, Bluetooth applications, wireless computer networks, etc.
If many devices sharing the wireless channel use the channel for sending data packets during a relatively busy time period, the chance increases that a particular device detects a signal in the channel, thereby reducing the chance that a particular signal can be transmitted after only a few iterations of the detecting step. Further, a particular device might be trapped in an indefinite waiting loop. For real time applications, such as real time low-latency audio and/or video applications, such effects might induce undesired quality loss of signals, such as drop-outs and/or stottering.
Further, contention free protocols are known defining scheduled time slots allowing specific devices to transmit data packets satisfying predefined characteristics into a shared wireless channel.